This invention relates to a sealing structure for a bearing.
For lubricating bearings in high speed spindles such as a grinding wheel spindle, oil-fog lubrication is generally used, in which oil mist is poured from the outside toward bearings. This lubrication has remarkable lubricating and cooling effect in comparison with other lubricating methods, and further is said to have some sealing effect because oil mist spouts out, through the gap between the journal of the spindle and the opening surrounding the journal.
But the oil mist amount spouting out through the gap is practically not enough for sufficient sealing, particularly in case of an internal grinder which uses high pressure coolant pouring into the working area. Pressured coolant is apt to penetrate into the bearings, overcoming oil mist. The penetration of coolant remarkably shortens the bearing life.
Further, recent centerless workpiece holders for internal grinders use hydrostatic pressure. This pressure causes pressurized liquid for work holding to penetrate into the bearings because the liquid pours directly toward the spindle nose.
For solving the above problem, the application of sealing means of mechanical seal, oil seal or the like is not preferable on account that perfect and reliable sealing and its maintenance could not be expected in such high pressure fluid atmosphere as described above.